Currently, most flyback switching power supplies uses a PWM control work mode to realize outputting constant voltage. Due to existing PWM control is controlling the peak current with a fixed frequency, when the duty ratio is more than 50%, the input voltage and loading condition are fixed, although inductance peak detection current is constant, but the inductance current appears a disturbance ΔI0, resulting in a bigger disturbance ΔI1 in the next period, then a current oscillation is formed to cause unstable output voltages. Therefore, manufacturing the flyback switching power supply needs the high voltage electrolytic capacitor to filter the rectified voltage, to make the output voltage of the flyback switching power supply stable.
The high voltage electrolytic capacitor enables the current to deliver leading current, and prevents the current and the voltage from homo-phase supply power, wasting the electricity.